On the heels of today’s MacBook Pro unveiling, Apple announced that it would be making a preview of Mac OS X 10.7 — codenamed Lion — available to developers. The company writes that Lion “takes some of the best ideas from iPad and brings them back to the Mac.” Apple details several, previously disclosed, features — such as Mission Control, Launchpad, and multitouch gestures — along with a handful of new, unannounced feature additions:

A new version of Mail, with an elegant, widescreen layout inspired by the iPad; Conversations, which automatically groups related messages into one easy to read timeline; more powerful search; and support for Microsoft Exchange 2010;

AirDrop, a remarkably simple way to copy files wirelessly from one Mac to another with no setup;

Versions, which automatically saves successive versions of your document as you create it, and gives you an easy way to browse, edit and even revert to previous versions;

Resume, which conveniently brings your apps back exactly how you left them when you restart your Mac or quit and relaunch an app;

Auto Save, which automatically saves your documents as you work;

The all new FileVault, that provides high performance full disk encryption for local and external drives, and the ability to wipe data from your Mac instantaneously; and

We have all been waiting to see what Apple has in store for the next major milestone in Mac OS X, and just now, at Apple’s “Back to the Mac” event, Steve Jobs has given us a preview of Mac OS X 10.7 Lion. The big thing here, as Steve puts it, is the joining of OS X with the best features found in iOS. Here are some of the biggest features previewed in Lion: